— 565 —
Existence not required to make it real.
      §8. For the attaining of Knowledge and Certainty it is requisite,
that we have determined Ideas: and to make our Knowledge real, it
is requisite, that the Ideas answer their Archetypes. Nor let it be
— 566 —
wondred, that I place the Certainty of our Knowledge in the Con-
sideration of our Ideas, with so little Care and Regard (as it may
seem) to the real Existence of Things: Since most of those Discourses,
which take up the Thoughts and engage the Disputes of those who
pretend to make it their Business to enquire after Truth and Cer-
tainty, will, I presume, upon Examination be found to be general
Propositions, and Notions in which Existence is not at all concerned.
All the Discourses of the Mathematicians about the squaring of a
Circle, conick Sections, or any other part of Mathematicks, concern
not the Existence of any of those Figures: but their Demonstrations,
which depend on their Ideas, are the same, whether there be any
Square or Circle existing in the World, or no. In the same manner,
the Truth and Certainty of moral Discourses abstracts from the
Lives of Men, and the Existence of those Vertues in the World,
whereof they treat: Nor are Tully’s Offices less true, because there
is no Body in the World that exactly practises his Rules, and lives
up to that pattern of a vertuous Man, which he has given us, and
which existed no where, when he writ, but in Idea. If it be true in
Speculation, i.e. in Idea, that Murther deserves Death, it will also be
true in Reality of any Action that exists conformable to that Idea of
Murther. As for other Actions, the Truth of that Proposition con-
cerns them not. And thus it is of all other Species of Things, which
have no other Essences, but those Ideas, which are in the Minds
of Men.
Locke Hum IV, 4, §8, pp. 565-566